You will see from this http://www.arhf.nl/images/logo-idea.gif idea that all four letters have an upper and a lower part. The lines separating upper and lower could be connected to each other in the form of a wave.

From the beginning of the first wave to the end of the last half a circle could be drawn below the four letters.

The line of the circle should not be visible, but from the line of the wave down the colour (possibly blue?) could get thinner and thinner until it disappears.

In this way the logo includes both the idea of the wave (fluid, dilution, resonance) as also the idea of the circle (wholeness, healing, globule).

This is just one idea. Would like to work in this direction but am open to and would appreciate your ideas!